Visa Stamping from Canada/ Mexico

Hello All,

I had my visa interview in Montreal consulate on 9th Feb. This was my f1-h1b stamping. The VO just asked me the following
1. Why montreal
2.Job role
3.How long have you been working for this employer
4. Do you have any trouble entering US
5. Highest level of education

After that, she asked for my resume and gave a 221g white form and told me it will take additional 3-4 weeks. I asked if there is any particular reason, she told me its the procedure.

I came back to the hotel and checked my status on CEAC website and to my surprise, my case was created on Feb 7th even though my interview was on 9th Feb. Is that normal??

My case keeps getting updated every 3 days but still under AP. Does anyone know how long it takes?

One more interesting point I noticed was that the VO took my DS160 approval page and wrote "221g M." Does anyone know what it means? is it Visa Mantis?

I am really worried when this processing will end.

Any thoughts would be helpful

Thanks